Hand held cutting tools are generally of two basic types; hand held knives and hand held saws. The basic design for the knife and saw are similar i.e. an elongated blade is provided with a handle at one end. The basic operation for both is also similar i.e., the blade is drawn back and forth across the desired cutting line while pressure is applied on the blade by a pivotal urging of the operators wrist. The cutting action, however, is quite different. The knife utilizes a continuous cutting edge and slices through and thereby separates the material being cut, while the saw has teeth that individually bite into and remote bits of material thereby digging a trench or kerf as it is commonly called.
The smooth precise cutting action of a knife is highly desireable, but for many applications the knife is simply unsuitable. For example, consider a large tree limb. The sharp edge of the knife will easily slide into the wood but only to a very shallow depth. As the blade enters the cut, the cut has to widen. Wood is "elastically" compressable (more or less depending on the type of wood) and thus penetration is permitted simply by the sides of the blade forcing compression of the wood fibers to thereby enlarge the cut. However, as more of the blade is forced into the cut, the cumulative effect of the resistance by the wood member to this compression very quickly renders it very difficult for the operator to continue cutting.
The hand held saw, having its blade edge made up of a sequence of sharp points, (referred to as teeth) cuts a trench that allows free entry of the blade. Typically, the cutting action of the saw involves a drawing of the saw blade coupled with forward pivoting of the wrist to achieve penetration of the teeth. The teeth dig in and pull loose in a rapidly repetitive action, and in the process, wood particles are ripped or torn loose from the wood member. As the saw teeth are worked back and forth in the cut, the trench is increased until the desired severing of the wood member is accomplished. This cutting action will be herein referred to as stutter cutting.
A major problem with the sawing blade is that at least in start up, the stutter cutting makes it difficult to hold the blade on the desired line of cut. This difficulty is referred to as the saw's tendency to skate and is a major cause of minor accidents experienced by operators placing their off hand too close to the desired line of cut. Also, the cut is ragged, the cutting efficiency is poor, and using the saw is uncomfortable and often a difficult task for the operator. These problems can be reduced by reducing the space between the teeth (depth and length) but to do so limits the ability of the saw to remove the particles and this undesirably effects the saws cutting capabilities.